329 research outputs found
Liquefied Natural Gas for Trucks and Buses
Liquefied natural gas (LNG) is being developed as a heavy vehicle fuel. The reason for developing LNG is to reduce our dependency on imported oil by eliminating technical and costs barriers associated with its usage. The U.S. Department of Energy (DOE) has a program, currently in its third year, to develop and advance cost-effective technologies for operating and refueling natural gas-fueled heavy vehicles (Class 7-8 trucks). The objectives of the DOE Natural Gas Vehicle Systems Program are to achieve market penetration by reducing vehicle conversion and fuel costs, to increase consumer acceptance by improving the reliability and efficiency, and to improve air quality by reducing tailpipe emissions. One way to reduce fuel costs is to develop new supplies of cheap natural gas. Significant progress is being made towards developing more energy-efficient, low-cost, small-scale natural gas liquefiers for exploiting alternative sources of natural gas such as from landfill and remote gas sites. In particular, the DOE program provides funds for research and development in the areas of; natural gas clean up, LNG production, advanced vehicle onboard storage tanks, improved fuel delivery systems and LNG market strategies. In general, the program seeks to integrate the individual components being developed into complete systems, and then demonstrate the technology to establish technical and economic feasibility. The paper also reviews the importance of cryogenics in designing LNG fuel delivery systems
Microwave whirlpools in a rectangular-waveguide cavity with a thin ferrite disk
We study a three dimensional system of a rectangular-waveguide resonator with
an inserted thin ferrite disk. The interplay of reflection and transmission at
the disk interfaces together with material gyrotropy effect, gives rise to a
rich variety of wave phenomena. We analyze the wave propagation based on full
Maxwell-equation numerical solutions of the problem. We show that the
power-flow lines of the microwave-cavity field interacting with a ferrite disk,
in the proximity of its ferromagnetic resonance, form whirlpool-like
electromagnetic vortices. Such vortices are characterized by the dynamical
symmetry breaking. The role of ohmic losses in waveguide walls and dielectric
and magnetic losses in a disk is a subject of our investigations
Controlled nanochannel lattice formation utilizing prepatterned substrates
Solid substrates can be endued with self-organized regular stripe patterns of
nanoscopic lengthscale by Langmuir-Blodgett transfer of organic monolayers.
Here we consider the effect of periodically prepatterned substrates on this
process of pattern formation. It leads to a time periodic forcing of the
oscillatory behavior at the meniscus. Utilizing higher order synchronization
with this forcing, complex periodic patterns of predefined wavelength can be
created. The dependence of the synchronization on the amplitude and the
wavelength of the wetting contrast is investigated in one and two spatial
dimensions and the resulting patterns are discussed. Furthermore, the effect of
prepatterned substrates on the pattern selection process is investigated
Dynamics of a thin liquid film with surface rigidity and spontaneous curvature
The effect of rigid surfaces on the dynamics of thin liquid films which are
amenable to the lubrication approximation is considered. It is shown that the
Helfrich energy of the layer gives rise to additional terms in the
time-evolution equations of the liquid film. The dynamics is found to depend on
the absolute value of the spontaneous curvature, irrespective of its sign. Due
to the additional terms, a novel finite wavelength instability of flat rigid
interfaces can be observed. Furthermore, the dependence of the shape of a
droplet on the bending rigidity as well as on the spontaneous curvature is
discussed.Comment: 4 pages, 5 figure
Probing La(0.7)Sr(0.3)MnO3 multilayers via spin wave resonances
La(0.7)Sr(0.3)MnO3/BiFeO3 and La(0.7)Sr(0.3)MnO3/PbZr20Ti80O3 epitaxial
heterostructures have been grown on SrTiO3 substrates. Spin wave resonances are
used to study interface properties of the ferromagnetic La(0.7)Sr(0.3)MnO3. We
find that the addition of the BiFeO3 or PbZr20Ti80O3 causes out-of-plane
surface pinning of the La(0.7)Sr(0.3)MnO3. We are able to place new limits on
the exchange constant D of La(0.7)Sr(0.3)MnO3 grown on these substrates and
confirm the presence of uniaxial and biaxial anisotropies caused by the SrTiO3
substrate.Comment: 7 pages, 5 figures, 3 table
The proteasome lid triggers COP9 signalosome activity during the transition of Saccharomyces cerevisiae cells into quiescence.
The class of Cullin–RING E3 ligases (CRLs) selectively ubiquitinate a large portion of proteins targeted for proteolysis by the 26S proteasome. Before degradation, ubiquitin molecules are removed from their conjugated proteins by deubiquitinating enzymes, a handful of which are associated with the proteasome. The CRL activity is triggered by modification of the Cullin subunit with the ubiquitin-like protein, NEDD8 (also known as Rub1 in Saccharomyces cerevisiae). Cullin modification is then reversed by hydrolytic action of the COP9 signalosome (CSN). As the NEDD8– Rub1 catalytic cycle is not essential for the viability of S. cerevisiae, this organism is a useful model system to study the alteration of Rub1–CRL conjugation patterns. In this study, we describe two distinct mutants of Rpn11, a proteasome-associated deubiquitinating enzyme, both of which exhibit a biochemical phenotype characterized by high accumulation of Rub1-modified Cdc53–Cullin1 (yCul1) upon entry into quiescence in S. cerevisiae. Further characterization revealed proteasome 19S-lid-associated deubiquitination activity that authorizes the hydrolysis of Rub1 from yCul1 by the CSN complex. Thus, our results suggest a negative feedback mechanism via proteasome capacity on upstream ubiquitinating enzymes
Thermomagnetic instability in hot discs
A linear stability analysis of ionized discs with a temperature gradient and
an external axial magnetic field is presented. It is shown that both
hydromagnetic and thermomagnetic effects can lead to the amplification of waves
and make discs unstable. The conditions under which the instabilities grow are
found and the characteristic growth rate is calculated. The regimes at which
both the thermomagnetic and magnetorotational instabilities can operate are
discussed.Comment: 6 pages, 1 figure, accepted for the publication in MNRA
The DOE/NREL Environmental Science Program
This paper summarizes the several of the studies in the Environmental Science Program being sponsored by DOE's Office of Heavy Vehicle Technologies (OHVT) through the National Renewable Energy Laboratory (NREL). The goal of the Environmental Science Program is to understand atmospheric impacts and potential health effects that may be caused by the use of petroleum-based fuels and alternative transportation fuels from mobile sources. The Program is regulatory-driven, and focuses on ozone, airborne particles, visibility and regional haze, air toxics, and health effects of air pollutants. Each project in the Program is designed to address policy-relevant objectives. Current projects in the Environmental Science Program have four areas of focus: improving technology for emissions measurements; vehicle emissions measurements; emission inventory development/improvement; ambient impacts, including health effects
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The DOE/NREL Environmental Science and Health Effects Program - An Overview
This paper summarizes current work in the Environmental Science and Health Effects (ES and HE) Program being sponsored by DOE's Office of Heavy Vehicle Technologies (OHVT) through the National Renewable Energy Laboratory (NREL). The program is regulatory-driven, and focuses on ozone, airborne particles, visibility and regional haze, air toxics, and health effects of air pollutants. The goal of the ES and HE Program is to understand atmospheric impacts and potential health effects that may be caused by the use of petroleum-based and alternative transportation fuels. Each project in the program is designed to address policy-relevant objectives. Studies in the ES and HE Program have four areas of focus: improving technology for emissions measurements; vehicle emissions measurements, emission inventory development/improvement; and ambient impacts, including health effects
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